This application is related to and claims priority from Japanese Patent Application No. Hei. 11-254490 filed on Sep. 8, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a blower unit for a vehicle air conditioner, which reduces an air-blowing noise transmitted into a passenger compartment through an inside air introduction port.
2. Description of Related Art
In a conventional blower unit described in U.S. Pat. No. 5,836,813, plural ribs for irregularly reflecting noise are disposed on a concave inner surface of a rotary door to reduce noise. However, because the plural ribs having the same height simply protrude from the concave inner surface of the rotary door a connection line connecting top ends of the plural ribs does not correspond to a main flow of inside air flowing from an inside air introduction port to a suction port of a fan, and the main flow of inside air is disturbed by the plural ribs. Therefore, flow disturbance noise of inside air is caused in the blower unit when an air amount blown by the fan is increased during an inside air introduction mode. SUMMARY OF THE INVENTION
In view of the foregoing problems, it is an object of the present invention to provide a blower unit for a vehicle air conditioner, which effectively prevents both reflection noise on a door inner surface and flow disturbance noise of inside air.
According to the present invention, in a blower unit for a vehicle air conditioner, a rib member is disposed on an inner surface of a switching door to irregularly reflect noise generated by a fan during an inside air introduction mode where the switching door opens an inside air introduction port and closes an outside air introduction port, and the rib member is disposed so that a top end of the rib member is along a main flow of air flowing from the inside air introduction port toward a suction port of the fan during the inside air introduction mode. Therefore, air-blowing noise generated by the fan can be irregularly reflected by the rib member to be reduced. Further, because the top end of the rib member is positioned along the main flow of inside air flowing from the inside air introduction port toward the suction port of the fan, the main flow of inside air is not disturbed by the top end of the rib member, and flow disturbance noise of inside air can be restricted even when an amount of inside air introduced from the inside air introduction port into the suction port of the fan is increased.
Preferably, the rib member includes plural ribs protruding from the inner surface of the switching door toward an inner side of the inside/outside air switching box during the inside air introduction mode, and top ends of the ribs are disposed along the main flow of air flowing from the inside air introduction port during the inside air introduction mode. Therefore, the blower unit effectively prevents both the reflection noise on the inner surface of the switching door and the flow disturbance noise of inside air.
Further, in the blower unit, when a supplementary door separated from the switching door is disposed to open and close a supplementary inside air port, a top end of the supplementary inside air door is disposed along the main flow of air flowing from the inside air introduction port during the inside air introduction mode. Therefore, the top end of the supplementary inside air door does not disturb the main flow of inside air, and flow disturbance noise due to the top end of the supplementary inside air door is prevented.
Even when a rotary door is used as the switching door so that an opening area of the inside air introduction port is increased, the flow disturbance noise of inside air can be effectively restricted while the air-blowing noise generated by the fan can be reduced.